ByeongByeong--Joo Lee Joo Lee - POSTECH · Scope CVD 1. Too much changeable results depending on...

Byeong-Joo Leewww.postech.ac.kr/~calphad

ByeongByeong--Joo LeeJoo Lee

POSTECH POSTECH -- MSEMSE

[email protected]@postech.ac.kr

ScopeScope

CVD

1. Too much changeable results depending on the condition

2. Beyond Scientific Explanation for long time

3. Process development has been mostly empirical

Approach (by Nong Moon Hwang, KRISS/SNU)

1. How to define the driving force of CVD

2. Low pressure synthesis of Diamond


2. Low pressure synthesis of Diamond

3. Charged Cluster Model in CVD

References

N.M. Hwang et al., Diamond and Related Materials, 1 (1992)

191-194.; 3 (1993) 163-167.

N.M. Hwang et al., J. Crystal Growth 135 (1994) 165-171;

143 (1994) 103-109; 160 (1996) 87-97; 160 (1996) 98-103;

162 (1996) 55-68.

Homogeneous NucleationHomogeneous Nucleation

Nucleation of liquid from vapor

assume spherical nucleus


Homogeneous NucleationHomogeneous Nucleation


CVD Diamond CVD Diamond -- N.M. Hwang et al., J. Crystal Growth 162, 55 (1996)N.M. Hwang et al., J. Crystal Growth 162, 55 (1996)


Diamond deposited on silicon substrate Soot deposited on the iron substrateDiamond deposited on silicon substrate Soot deposited on the iron substrate

CVD Si CVD Si -- N.M. Hwang et al., J. Crystal Growth 218, 27 (2000)N.M. Hwang et al., J. Crystal Growth 218, 27 (2000)


CVD Si Nanowire CVD Si Nanowire -- N.M. Hwang et al., J. Crystal Growth 218, 33 (2000)N.M. Hwang et al., J. Crystal Growth 218, 33 (2000)


※ Example: Deposition of Silicon CarbideSiH4 + CH4 = SiC + 4H2

Driving force of CVD DepositionDriving force of CVD Deposition


Diamond formation with simultaneous graphite etchingDiamond formation with simultaneous graphite etching

in low pressure synthesis of diamondin low pressure synthesis of diamond

Thermodynamic ParadoxThermodynamic Paradox


∆−

∆=

kT

G

kT

GOqI co

**

exp

σπ

πµ 3/2

3/2

4

34 nnG solidgas

Ω+∆=∆ →

323216 ΩΩ σπσπ

Nucleation of clusters in gas phase Nucleation of clusters in gas phase -- Diamond/GraphiteDiamond/Graphite

∆−∆⋅=

kT

GGA

I

I diagra

gra

dia **

exp


2

32

2

32

**

)(3

16

)(3

16

diagas

diadia

gragas

gragra

diagra GG→→ ∆

Ω−

∆

Ω=∆−∆

µσπ

µ

σπ

The nucleation ratio is very sensitive to the variation of the surface energy

ranging from 1010 to 10-6 with σdia = 3.7 and 4.1 J/m2

at 1200K and σgra = 3.1 J/m2

→ There must be some factor that modifies the surface energy of diamond

→ Creation of the Charged Cluster Model

ByeongByeong--Joo Lee Joo Lee - POSTECH · Scope CVD 1. Too much changeable results depending on...

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